Final Output-Level Calibration
Dolby
®
CP750 Digital Cinema Processor Manual
51
Equalization
facilities
for
the
subwoofer
channel
are
different
than
for
the
other
channels.
The
process
in
this
manual
is
designed
to
correct
the
principal
room
resonance
in
the
operating
range
of
the
subwoofer.
The
subwoofer
equalizer
is
a
cut
‐
only
filter,
with
adjustable
center
frequency
(25
to
125
Hz),
Q
(center
width,
selectable
among
four
values),
and
amount
of
cut
(0
to
12
dB).
After
all
the
full
‐
range
channels
have
been
equalized,
follow
these
steps:
1.
Click
LFE
to
make
it
the
active
channel.
2.
Using
the
slider
reduce
Cut
to
0
dB
.
This
disables
EQ
so
that
you
can
determine
the
low
‐
frequency
resonant
peak
to
be
equalized.
Note
the
band
where
the
unequalized
peak
appears.
3.
Using
the
slider
increase
Cut
to
its
maximum,
12
dB.
Using
the
Center
slider
moves
the
dip
in
the
frequency
response
along
the
frequency
axis
of
the
RTA
display.
4.
Adjust
the
center
frequency
so
that
the
center
of
the
dip
is
in
the
same
band
as
the
peak
displayed
in
the
previous
unequalized
frequency
response.
5.
Using
the
Cut
slider,
slowly
reduce
the
amount
of
cut
to
flatten
the
dip.
The
center
of
the
dip
should
be
at
the
same
level
as
the
skirts.
6.
Click
to
check
other
Q
values
for
the
flattest
possible
frequency
response.
6.7
Final Output-Level Calibration
Once
room
equalization
is
complete,
the
sound
pressure
level
in
the
theatre
can
be
set
accurately.
6.7.1
Main Channels
If
a
microphone
multiplexer
is
being
used
in
your
auditorium,
move
Mic
1
to
room
center
two
‐
thirds
back
from
the
screen.
1.
Click
the
Room
Levels
tab
to
activate
it.
2.
Using
the
sliders,
set
L,
C,
R
to
85 dB,
and
the
surround
channels
to
82 dB.
6.7.2
Subwoofer Channel Level
Whereas
the
final
sound
pressure
levels
of
the
main
audio
channels
are
ideally
adjusted
with
a
single
microphone
two
‐
thirds
back
from
screen
at
room
center,
the
subwoofer
channel
level
is
best
adjusted
with
the
microphone
multiplexer
cycling
(if
available).
1.
First
complete
the
center
channel
equalization
and
level
adjustment.
2.
On
the
Channel
Tune
tab,
click
LFE
to
make
it
the
active
channel
and
select
Pink
Noise
as
the
Signal
Mode
.
3.
Use
the
slider
and
arrow
keys
to
achieve
an
average
level
of
+10
dB
as
indicated
on
the
spectrum
analyzer.
This
is
the
“digital”
level,
which
is
always
set
10
dB
higher
than
the
Center
channel.
Note:
Because
the
sound
pressure
level
calibration
was
performed
earlier,
a
recalibration
is
not
required
unless
the
microphone
placement
has
changed.
Repeat
the
steps
in
if
necessary.
Summary of Contents for CP750
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